1. Field of Invention
The invention relates to an electric drive control apparatus, an electric drive control method and a program therefor.
2. Description of Related Art
In a conventional electric drive unit which is mounted on a vehicle, for example, on an electric vehicle or an electric car, and which produces a torque of a drive motor which is an electrically operated machine, it is a practice to transmit the drive motor torque to the drive wheels to obtain a driving force.
Further, in an electric drive unit mounted on an electric vehicle or on a hybrid vehicle and transmits the engine torque or part of the engine torque to a generator (generator-motor) which is a first electrically operated machine and transmits the rest of the engine torque to the drive wheels, it is a practice to provide a planetary gear unit having a sun gear, a ring gear and a carrier, to couple the carrier to the engine, to couple the ring gear to the drive wheels, to couple the sun gear to the generator, and to transmit the rotation produced by the ring gear and by a drive motor which is a second electrically operated machine to the drive wheels to obtain a driving force.
In the generator and the drive motor, there are arranged a rotor which is allowed to freely rotate and has a pair of magnetic poles comprising permanent magnets of N-pole and S-pole, and a stator disposed on the outer side of the rotor in the radial direction and having stator coils of U-phase, V-phase and W-phase.
The electric car is furnished with a drive motor control apparatus as an electromechanical controller. The hybrid vehicle is furnished with a generator control apparatus and a drive motor control apparatus as an electrically operated machine control apparatus. Pulse width modulation signals of the U-phase, V-phase and W-phase generated by the electrically operated machine control apparatus are sent to an inverter, and phase currents generated by the inverter are fed, i.e., currents of the U-phase, V-phase and W-phase, to the stator coils to energize the drive motor thereby to obtain a drive motor torque, or to drive the generator to obtain a generator torque.
In the above drive motor control apparatus, for example, a feedback control is executed by the vector control operation on a d-q axis model by setting a d-axis in a direction of the magnetic pole pair of the rotor, and setting a q-axis in a direction at right angles to the d-axis. Therefore, the drive motor control apparatus detects currents fed to the stator coils, a magnetic pole position of the rotor and a DC voltage at the input of the inverter, converts the detected currents into a d-axis current and a q-axis current based on the magnetic pole position, and calculates a d-axis current instruction value and a q-axis current instruction value representing target values of the d-axis current and the q-axis current based on the DC voltage in order to bring a deviation between the d-axis current and the d-axis current instruction value to zero (0) and a deviation between the q-axis current and the q-axis current instruction value to zero (0) (see, for example, JP-A-5-130710).
In the above conventional electric drive unit, however, a current instruction value that cannot be realized is set if there exist errors in the sensors, such as a current sensor for detecting the current, a magnetic pole position sensor for detecting the magnetic pole position or a voltage sensor for detecting the DC voltage, or if there is a change in the device constants, such as counter electromotive force constant MIf of the drive motor, inductances Ld, Lq of the stator coils, and resistance Ra of the stator coils accompanying a change in the temperature.
In such a case, the voltage is saturated, a deviation occurs between a target drive motor torque TM* and a drive motor torque TM that is really produced, causing the driver to feel uncomfortable while traveling and making it difficult to drive the drive motor.